Project Summary Acute lymphoblastic leukemia (ALL) is the most common hematological malignancy in pediatric patients and the most frequent cause of cancer-related mortality before the age of 20. Current treatment strategies act by non-specific mechanisms that are incapable of achieving and maintaining remission in the nearly 1 out of 4 pediatric patients with therapy-resistant disease. While targeted therapies are not currently available for ALL patients, they could potentially improve patient outcomes by interfering with pathological cellular and molecular activities that facilitate resistance to multi-agent chemotherapy. Increased expression of protein kinase MEK7 and consequent amplification of downstream MAP kinase signaling have been identified as two such processes facilitating chemoresistance in T-cell ALL (T-ALL), rendering MEK7 an attractive target for T-ALL directed therapies. Unfortunately, there are no small molecules known to potently and selectively inhibit this MEK isoform. Leveraging our published platform for interrogating inhibitor selectivity across the MEK kinase family, we have designed and synthesized a lead compound exhibiting potent MEK7 inhibition. The objective of my present proposal is the further development and optimization of a potent and selective small molecule MEK7 inhibitor to chemically probe aberrant signaling in this arm of the MAPK pathway in T-ALL models. Our methodology entails a multifaceted approach employing strategies from disciplines spanning computational chemistry, organic synthesis, protein biochemistry, and molecular biology. Through these complementary modalities, we seek to gain new insight into the roles of the least understood MEK isoform in the molecular pathophysiology underlying T-ALL. Of utmost clinical significance, the studies in this proposal will survey the efficacy of direct MEK7 inhibitors as targeted therapies for T-ALL.